The Glowing Bridge
From Sonic Retro
The Glowing Bridge is a web site that exists purely to archive research on Sonic the Hedgehog prototype games. Although several of the sections are still under construction, the sections that are complete are thorough and factual, providing a mixture of research from various forums and sites.
Created by Qjimbo in late March, the site originally started off simply being a forum split, however since then it has gone much futher than that. See the S2B article for more information behind the backstory.